Extrusion machines have been used for many years to extrude both solid and tubular products and to apply a sheath or cladding over a core material. In many instances the extrusion temperature at which the sheath material is extruded is significantly greater than the melting point of the core material. Additionally, an adhesive, having a melting point lower than the extruded sheath material, is sometimes placed on the core material to aid in bonding the core material to the sheath. A difference in temperatures of the sheath and core materials can create such problems as the core material sticking to the extruded sheath or a premature activation of the adhesive.
When extruding an aluminum sheath over an insulating polymer core, such as in the manufacture of co-axial cable, the sheath material is normally extruded having a greater inner diameter than the outer diameter of the inner core. This results in the core material being loose and free to move within the sheath after the extrusion process. Once cool, the sheath and core go through a draw die which reduces the sheath O.D. and bonds the sheath to the inner core. During the drawing process the sheath is elongated. As the sheath is elongated, the core material must be free within the sheath to feed through the sheath as the sheath is drawn around it. If the core material adheres to the sheath prior to the sheath entering the draw die, the subsequent elongation of the sheath results in the core material breaking, rather than feeding through the sheath as desired.
Accordingly, it is the object of the present invention to provide an extrusion apparatus which sufficiently cools the core material prior to passing the core material through the extrusion assembly so that the precooling of the core material prevents the core from sticking to the extruded sheath to thereby avoid breakage of the core material during the drawing process.